Analysis of the turbulent flow and trailing vortices induced by new design grooved blade impellers in a baffled tank

Abstract U or V shaped grooves have shown reduction in energy and power consumption in blunt bodies immersed in turbulent streams. In this work, the performance of two new design turbines with four blades rotated 45°, one with U and the other with V grooved shape blades, were evaluated in a baffled stirred tank reactor and they were compared with the one of the regular 4PBT. The power consumption, mean velocities, turbulent kinetic energy production (TKE), energy dissipation rate (e) and trailing vortices induced by new design impellers with grooved walls and 4PBT were evaluated experimentally and modeled by detached eddy simulation (DES) approach, which has not been tested in blade walls with small perturbations. Validation of the results was carried out by PIV (Particle image velocimetry) experimental tests. The evolution of new and distinctive trailing vortices located in the upper and lower faces of the grooved new design impellers is presented. They were measured by angled resolved PIV technique, and visualized in three dimensions by the DES method. The V-grooves shaped impeller generated a larger region of influence of the turbulent kinetic energy along the discharge region than the other impellers. Moreover, presented higher mean dissipation rate levels for the most of the measured angles and induced higher number of trailing vortices in the blades vicinity than the other turbines. It was found that in a wide range of the Reynolds number (Re) (40 × 10 3 3 ) the dissipated power measured experimentally from shaft, presented reductions of the order of 6% and 4% for the U and V grooved new models, respectively, compared with that of the regular 4PBT impeller.